Ricky Barnes, whose anonymity in his chosen profession is reflected in a world ranking of 519, defied the physics of the swing and the expectations of most here as he maintained his challenge for what would be a stunning US Open victory.

As the rains abated on what has been dubbed the US Wide Open, the 28-year-old American shot a third-round 70, level-par, for a 54-hole score of 202, eight under, to take a one-shot lead over his compatriot Lucas Glover going into the final round of this benighted event. England's Ross Fisher was four shots further back in a tie for third alongside the former world No1 David Duval, who after an existential crisis that would have made Sartre proud has re-embraced the sport that made him famous.

A cavalry charge of players was one shot further adrift, including, ominously for those at the head of the field, Phil Mickelson. The left-hander looked like a man with a mission yesterday even if he occasionally stumbled over his own feet on his way to a third-round 69. A Mickelson victory is the dream scenario for television, for the Bethpage galleries, which adore him, and for those who like their sporting moments steeped in emotion.

Yet, if Mickelson will carry the overwhelming support of the watching world, Barnes should be credited for his efforts over the first 54 holes. His swing, as one wag had it, looks like Bambi on ice and his putting stroke is best observed through the cracks in your fingers, but he can play. He started yesterday's delayed third round at eight under par, one ahead of the field and was widely expected to collapse at the sight of his name atop the leaderboard. He did, but only to a limited degree.

An eagle on the par-five 4th lifted him to 11 under and into a select group of players who have been double digits under par at the US Open. This tournament is traditionally the most difficult major on the rota. It is not meant to be a cakewalk and it was not as Barnes reached the meat of his round, where he ran into a swamp of nerves. Bogeys at the 7th, the 10th – where he was lucky to find his tee shot – and the 12th portended an abject collapse but to his credit he fought back with a birdie on the par-five 13th to climb back to eight under par.

It is safe to assume that the hoi polloi of the US Golf Association, which likes its Open courses to be brutal and its national champions to be thoroughbreds, will have been disappointed at this turn of events. In all 14 players were at par or better after 54 holes. Among those was Tiger Woods, who had been a prohibitive favourite before a ball was struck.

Halfway through yesterday's third round the world No1 was three over par and 13 shots behind the leader. While others would have taken leave of the tournament Woods refused to slip the bonds of this US Open and three birdies on either side of the turn proved he is unparalleled in the art of chasing lost causes. He might even have played himself back into contention but, while his ball striking was wonderful, his putting was not and he somehow turned a 64 into a 68 – a good round but probably not enough.

Mickelson was another facing an ­improbable task. Yet at two under par after 54 holes he was by no means out of it. "I'm one good round away," the world No2 said, his eyes blazing with ambition. "I can shoot a lot of birdies and a 65, even if I make a couple of bogeys."

Of course he can but the difficulty will be quelling his habit of throwing away shots. The galleries were ecstatic as he birdied the 3rd, 7th and 8th. Less pleasing were three bogeys, and a double bogey at the 6th, where he drew a plugged lie under the lip of a greenside bunker and could only chip out sideways. It was thrilling stuff, a fairground ride disguised as a round of golf, and it continued all the way to the end, with a 40-foot birdie putt dropping at the 18th.

The responsibility of scaring the living daylights out of the runaway leader fell to others who have never scared anyone without the help of an inflated balloon and a hat pin – the likes of Mike Weir, Glover and, representing Europe, Ross Fisher. "If I had putted decently over the first three rounds I would be ridiculously under par," he said after signing for a one-under 69.